/*	$OpenBSD: fmt_scaled.c,v 1.20 2021/06/20 14:08:42 tb Exp $	*/

/*
 * Copyright (c) 2001, 2002, 2003 Ian F. Darwin.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * fmt_scaled: Format numbers scaled for human comprehension
 * scan_scaled: Scan numbers in this format.
 *
 * "Human-readable" output uses 4 digits max, and puts a unit suffix at
 * the end.  Makes output compact and easy-to-read esp. on huge disks.
 * Formatting code was originally in OpenBSD "df", converted to library routine.
 * Scanning code written for OpenBSD libutil.
 */
#include "compat.h"

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>

#include "util.h"

typedef enum {
  NONE = 0,
  KILO = 1,
  MEGA = 2,
  GIGA = 3,
  TERA = 4,
  PETA = 5,
  EXA = 6
} unit_type;

/* These three arrays MUST be in sync!  XXX make a struct */
static const unit_type units[] = {NONE, KILO, MEGA, GIGA, TERA, PETA, EXA};
static const char scale_chars[] = "BKMGTPE";
static const long long scale_factors[] = {
    1LL,
    1024LL,
    1024LL * 1024,
    1024LL * 1024 * 1024,
    1024LL * 1024 * 1024 * 1024,
    1024LL * 1024 * 1024 * 1024 * 1024,
    1024LL * 1024 * 1024 * 1024 * 1024 * 1024,
};
#define SCALE_LENGTH (sizeof(units) / sizeof(units[0]))

#define MAX_DIGITS (SCALE_LENGTH * 3) /* XXX strlen(sprintf("%lld", -1)? */

/* Convert the given input string "scaled" into numeric in "result".
 * Return 0 on success, -1 and errno set on error.
 */
int scan_scaled(char *scaled, long long *result) {
  char *p = scaled;
  int sign = 0;
  unsigned int i, ndigits = 0, fract_digits = 0;
  long long scale_fact = 1, whole = 0, fpart = 0;

  /* Skip leading whitespace */
  while (isascii((unsigned char)*p) && isspace((unsigned char)*p))
    ++p;

  /* Then at most one leading + or - */
  while (*p == '-' || *p == '+') {
    if (*p == '-') {
      if (sign) {
        errno = EINVAL;
        return -1;
      }
      sign = -1;
      ++p;
    } else if (*p == '+') {
      if (sign) {
        errno = EINVAL;
        return -1;
      }
      sign = +1;
      ++p;
    }
  }

  /* Main loop: Scan digits, find decimal point, if present.
   * We don't allow exponentials, so no scientific notation
   * (but note that E for Exa might look like e to some!).
   * Advance 'p' to end, to get scale factor.
   */
  for (;
       isascii((unsigned char)*p) && (isdigit((unsigned char)*p) || *p == '.');
       ++p) {
    if (*p == '.') {
      if (fract_digits > 0) { /* oops, more than one '.' */
        errno = EINVAL;
        return -1;
      }
      fract_digits = 1;
      continue;
    }

    i = (*p) - '0'; /* whew! finally a digit we can use */
    if (fract_digits > 0) {
      if (fract_digits >= MAX_DIGITS - 1)
        /* ignore extra fractional digits */
        continue;
      fract_digits++; /* for later scaling */
      if (fpart > LLONG_MAX / 10) {
        errno = ERANGE;
        return -1;
      }
      fpart *= 10;
      if (i > LLONG_MAX - fpart) {
        errno = ERANGE;
        return -1;
      }
      fpart += i;
    } else { /* normal digit */
      if (++ndigits >= MAX_DIGITS) {
        errno = ERANGE;
        return -1;
      }
      if (whole > LLONG_MAX / 10) {
        errno = ERANGE;
        return -1;
      }
      whole *= 10;
      if (i > LLONG_MAX - whole) {
        errno = ERANGE;
        return -1;
      }
      whole += i;
    }
  }

  if (sign)
    whole *= sign;

  /* If no scale factor given, we're done. fraction is discarded. */
  if (!*p) {
    *result = whole;
    return 0;
  }

  /* Validate scale factor, and scale whole and fraction by it. */
  for (i = 0; i < SCALE_LENGTH; i++) {

    /* Are we there yet? */
    if (*p == scale_chars[i] || *p == tolower((unsigned char)scale_chars[i])) {

      /* If it ends with alphanumerics after the scale char, bad. */
      if (isalnum((unsigned char)*(p + 1))) {
        errno = EINVAL;
        return -1;
      }
      scale_fact = scale_factors[i];

      /* check for overflow and underflow after scaling */
      if (whole > LLONG_MAX / scale_fact || whole < LLONG_MIN / scale_fact) {
        errno = ERANGE;
        return -1;
      }

      /* scale whole part */
      whole *= scale_fact;

      /* truncate fpart so it does't overflow.
       * then scale fractional part.
       */
      while (fpart >= LLONG_MAX / scale_fact) {
        fpart /= 10;
        fract_digits--;
      }
      fpart *= scale_fact;
      if (fract_digits > 0) {
        for (i = 0; i < fract_digits - 1; i++)
          fpart /= 10;
      }
      if (sign == -1)
        whole -= fpart;
      else
        whole += fpart;
      *result = whole;
      return 0;
    }
  }

  /* Invalid unit or character */
  errno = EINVAL;
  return -1;
}

/* Format the given "number" into human-readable form in "result".
 * Result must point to an allocated buffer of length FMT_SCALED_STRSIZE.
 * Return 0 on success, -1 and errno set if error.
 */
int fmt_scaled(long long number, char *result) {
  long long abval, fract = 0;
  unsigned int i;
  unit_type unit = NONE;

  /* Not every negative long long has a positive representation. */
  if (number == LLONG_MIN) {
    errno = ERANGE;
    return -1;
  }

  abval = llabs(number);

  /* Also check for numbers that are just too darned big to format. */
  if (abval / 1024 >= scale_factors[SCALE_LENGTH - 1]) {
    errno = ERANGE;
    return -1;
  }

  /* scale whole part; get unscaled fraction */
  for (i = 0; i < SCALE_LENGTH; i++) {
    if (abval / 1024 < scale_factors[i]) {
      unit = units[i];
      fract = (i == 0) ? 0 : abval % scale_factors[i];
      number /= scale_factors[i];
      if (i > 0)
        fract /= scale_factors[i - 1];
      break;
    }
  }

  fract = (10 * fract + 512) / 1024;
  /* if the result would be >= 10, round main number */
  if (fract >= 10) {
    if (number >= 0)
      number++;
    else
      number--;
    fract = 0;
  } else if (fract < 0) {
    /* shouldn't happen */
    fract = 0;
  }

  if (number == 0)
    strlcpy(result, "0B", FMT_SCALED_STRSIZE);
  else if (unit == NONE || number >= 100 || number <= -100) {
    if (fract >= 5) {
      if (number >= 0)
        number++;
      else
        number--;
    }
    (void)snprintf(result, FMT_SCALED_STRSIZE, "%lld%c", number,
                   scale_chars[unit]);
  } else
    (void)snprintf(result, FMT_SCALED_STRSIZE, "%lld.%1lld%c", number, fract,
                   scale_chars[unit]);

  return 0;
}

#ifdef MAIN
/*
 * This is the original version of the program in the man page.
 * Copy-and-paste whatever you need from it.
 */
int main(int argc, char **argv) {
  char *cinput = "1.5K", buf[FMT_SCALED_STRSIZE];
  long long ninput = 10483892, result;

  if (scan_scaled(cinput, &result) == 0)
    printf("\"%s\" -> %lld\n", cinput, result);
  else
    perror(cinput);

  if (fmt_scaled(ninput, buf) == 0)
    printf("%lld -> \"%s\"\n", ninput, buf);
  else
    fprintf(stderr, "%lld invalid (%s)\n", ninput, strerror(errno));

  return 0;
}
#endif
